With their II and III series getting rather long in the tooth, and the Lisa being rather pricey, Apple had to do something to get back into the small-business market. They did.

The Macintosh can be considered the very first commercially successful computer to use a GUI (Graphical User Interface). It was, however, not the first GUI based computer, the first GUI based computer ever sold was the Xerox Star 8010 in 1981.

It was launched a while after the Lisa and was a very attractive alternative to PC compatibles and their old MS-DOS, and text-based applications. After uncertain beginnings, it met with great success despite having no hard disk, single-sided floppy disks, no expansion slot and very little memory!

It was replaced later by the Macintosh 512 (the same but with 512 KB RAM) then later, by the Macintosh Plus.

The Macintosh 128 and Macintosh 512 were non-upgradeable, non-expandable in almost all departments, but especially with regard to memory. The 128 and 512 had memory chips soldered directly to the main logic board.

The original System file was designated 'Macintosh System 1.0'. Apple went as far as System 7 before changing the name to 'Mac OS'. The System/Finder suite was designated 'Macintosh System Software 0.0.'. It wasn't until System 6 that the System file version and System Software designation coincided.

There were also two variants of Macintosh 512K. The 512K was shipped with a 400K floppy drive and 64 KB ROM, which did not support hierarchical file systems. The 512K Enhanced was shipped with 128 KB of ROM, an 800K floppy drive, and supported HFS right out of the box.